US2619161A - Component checking burner control apparatus - Google Patents

Description

Nov. 25, 1 952 .1. E. LUNDBERG 2,619,151

COMPONENT CHECKING BURNER CONTROL APPARATUS Filed Sept. 15, 1950 2 OVERLAPPING4 I 22 .IE. 2 p24 IN V EN TOR. JOHN E. LUNDBERG M/VM Patented Nov. 25, 1952 COMPONENT CHECKING BURNER CONTROL APPARATUS John E. Lundberg, Minneapolis, Minn, assignor: to Minneapolis-Honeywell Regulator Company," Minneapolis, Minn, a corporation of Delaware Applicationseptembcr 15, 1950, Serial N 0. 184,975 "I 6 Claims.

The present invention relates to animproved fuel burner control apparatus. More particular ly, the present invention is concerned witha cn-' tr-olapparatus which wil1 maintain a controlled fuelburner inoperative" in the event there is a flamefailure or a false indication of flame.

In present day fuel burner controls, it has been found desirable 'to provide safety devices which Will render the controlled. burner inoperative in the event that combustion fails to take place when the burner is started, in the event that combustion fails after having once been initiated, or in the event that the control apparatus indicates falsely that there is combustion taking place at the burner. In a Patent 2,537,294 of John M. Wilson for Component Checking Circuit For Burner Control Apparatus, and assigned to the same assignee as the present invention, there is disclosed an arrangement where a fuel burner is rendered inoperative in the event the-re is a flame failure or in the event that there isv a.

false indicationof flame by the flame detecting device. In either event, the burner control will maintain the burner inoperative until such time as the fault has been. removed from the control apparatus and it is possible to have sustained combustion without having the safety cutout device of the apparatus shut the system down.

The present invention is concerned with a burner control apparatus of the type disclosed in the Wilson applicationand constitutes an improvement thereof. The present invention provides a special arrangement of the electrical circult which will give maximum safe operation under conditions where there is a tendency for contacts of .a flame responsive switching device to become dirty or contaminated. This is accomplished by so interconnectingswitch contacts of the control apparatus that, upon the presence of combustion an actuator of a-safety cutout device of the apparatus-is open circuited whenflame is present and, when flame is not present, it is impossible to initiate burner operation or energizatio-n of the burner control device unless-- Another object of'thepresent invention is to providewan improved @b'urner control apparatus wherein. maximum -safe operation may be 010- 2: V tamed under circumstances where the flame switch contacts may become dirty or contamihated? stillanother object of the present invention-is to'provide-a new and improvedburner controlapparatus wherein 'a-safety cutout device having an electric actuator thereforis provided for shutting down the burner apparatus in the event there is a flame failureor a false indication'of flame and open'circuiting the actuator of the safety cutout device when the apparatus isop erating properly.

These and other objectsfof the present invention will be understood uponlar-consideration of thefollowing specification, claims, and. the. drawings appended hereto,of which;

Figure 1 is a diagrammatic showing of the. present invention, and

Figure-2 shows the circuit. of Figure .1 insimplified form.

Referring to Figural, there. iscshown afuel burner H] which is. arranged to becontrolledby a thermostatic device .1! acting through appro--- priate control circuits in. a control: device'indisated generally by the numeral I2. A-photocell- I 3 is also used to affect the-operation of the control circuits within the housing and to effect burn- -er shutdown conditionswhen vthere-hasbeen a: flame failure with the .burnerin operation.-

Referring to. the controlcircuits withinthe housing r 12, the numeral l5 :representsa power transformer which supplies. power. to the subject control circuit This;..tr.ansformer comprises a primary winding, 15,.a secondary winding I1, and a further secondary winding 18. The secondary winding I1 is tapped at 19c The winding l1 sup. plies power to effect the operation of a control. relay 2!). ThiscontrolrelayZO comprises are-1 lay coil 2!, a pair of switch blades 22 and23, and.

.switch contacts 2 25.and 26.. When the relay.

coil 2l is deenergized, the switch blades 22 and 23 Y are normally biased out of engagement. by means not shown, from the contacts 24 and 26 and the blade 22 is biased into engagement. with the con.- tact 25.

Also included in the energizingcircuits of the relay 2!] is a safety cutout device 30. Thislcutout device 30 comprises a pair ofswitcheontacts 3! and 32 which are normally maintained in.en-'- gagement by a bimetallic member 33. For actu-. ating or warping the bimetallic member 33, a" heater 34 is provided and is mounted adjacent the bimetal. A reset operator-35 is'providedfor'" moving the contacts 3! and 32- 'into engagement I Z after the heater 34-hascaused'the bimetal 33 to move out from under the contacts 3| and 32 to permit the same to open.

The secondary winding i8 is used to supply power to a suitable flame detection device of the electronic type which may be of the type disclosed in the R. S. Feigal Patent 2,556,961 assigned to the same assignee as the present invention. The subject flame detector is so arranged that an output control relay, such as relay 42 will move to the energized position whenever a flame is detected at the burner In by the photoelectric device l3. The relay 42 comprises a relay coil 43, a switch blade 44 normally biased out of engagement with a resilient contact 45, a switch blade 46 normally biased into engagement with a resilient contact 41, and a switch blade 48 that is normally biased into engagement with an associated contact 49. The switch blades 44 and 46 and their associated contacts 45 and 41 are so arranged that the contacts are overlapping when the relay moves from the deenergized to the energized position or from the energized to the deenergized position. In other words, when the relay 42 becomes energized the switch blade 44 will move into engagement with the contact 45 before the switch blade 46 moves out of engagement with its associated contact 41.

If desired. a suitable ignition device 50 may be provided at the burner I0. However, the apparatus may be utilized with controls which have constant ignition or ignition by standing pilot flames.

Operation In considering the operation of the present apparatus, assume first that the thermostatic device H is not demanding operation of the burner l and the apparatus is in the completely deenergized position. When in the deenergized position the apparatus will be shown as it is in the drawing in Figure 1.

Upon the s ace wherein the thermostatic device H is located cooling, to indicate a need for burner operation, the contacts of the thermostatic device will close and an energizing circuit for the relay 20 will be completed. This energizing circuit may be traced from the upper terminal of secondary I1 throu h safety cutout device contacts 32 and 3|, conductor 60, relay coil 2|, conductor 6|, thermostatic device conductor 62, switch contact 41, switch blade 46, conductor 63, conductor 64. heater 34 and conductor 65 back to the lower terminal of the secondary ll. When the circuit is completed, the relay coil will cause the switch blades 22 and 23 to move into engagement with their associated contacts 24 and 26 respectively. When the switch blade 23 engages contact 26, an energizing circuit is completed to the burner In. This circuit may be traced from an input power line 70 through conductor 1|, switch contact 26, switch blade 23, conductor 12, burner I0, and conductor 13 back to the other input power line 15. An energizing circuit will also be completed to the ignition device 50 and this energizing circuit may be traced from the input power line 19 through conductor 1|, switch contact 26, switch blade 23, conductor 12, switch blade 48, switch contact 49, conductor 16, ignition device 50, and conductor 13 back to the other input power line 15.

As soon as the burner flame is established at the burner l0 and the same is detected by the photocell I3, the flame detection device 40 will be operative to energize the relay 42. When the relay 42 becomes energized switch blades 44 and 46 will be moved from the deenergized position and, since the contacts are overlapping, the electrical circuits associated therewith will remain closed until such time as the switch blade 44 engages contact 45. When the switch blade 44 engages contact 45 a holding circuit for the relay 20 is established and this holding circuit includes the switch blade 22 and contact 24 of the relay 2!. The holding circuit may be traced from the upper terminal of the secondary I! through switch contacts 32 and 3|, conductor 60, relay coil 2|, conductor 6|, thermostatic device switch contact 24, switch blade 22, switch contact 45, switch blade 44, and conductor 18 back to the tap IS on secondary When the switch blade 22 moved out of engagement with contact 25 and the switch blade 46 moved out of engagement with contact 41, the energizing circuit to the heater 34 was broken so that the heater will no longer be effective to tend to warp the bimetal 33 and cause opening of the contacts 3| and 32. When. the switch blade 48 moved out of engagement with contact 49, the energizing circuit to the ignition device 50 was broken.

The apparatus is now in the operating position and, when in the operating position, the safety switch heater will be open circuited to prevent shutting down of the apparatus and the apparatus will remain in this mode of operation until such time as there is no longer a call for operation of the burner by the thermostatic device II or there is a flame failure at the burner. The operation upon a flame failure will be considered below. If the thermostatic device II no longer indicates a need for operation of the burner, the energizing circuit to the relay 20 will be open circuited upon the opening of the thermostatic device contacts. As soon as the relay 20 becomes deenergized, the switch blades 22 and 23 will move to the deenergized position and the burner circuit will be interrupted. As soon as the burner circuit is interrupted the flame will no longer be detected by the flame detector 40 and the relay 42 will move to the deenergized position. As soon as the relay 42 is deenergized the apparatus will return to the position in which it is shown upon the drawing in Figure 1.

Operation upon flame failure In considering the operation upon flame failure, first consider that there has been a demand for burner operation by the closing of the contacts to the thermostatic device II. The closing of these contacts will cause the energization of the relay 20 by a circuit which has been traced above. When the relay 20 does become energized the burner l0 and ignition device 50 will become energized, as also traced above. It will be recalled that the energizing circuit for the relay 26 can be traced through the heater 34 of the safety cutout device 30. This energizing circuit is more conveniently shown in Figure 2 where the circuit may be traced from the right hand terminal of the secondary I! through the safety cutout contacts 3| and 32, relay coil 2|, thermostatic device switch contacts 41 and 46, and heater 34 back to the left hand terminal of the secondary l1. When the relay 20 becomes energized the contacts 22 and 24 will move into engagement and the contacts 22 and 25 will move out of engagement. This latter movement of the contacts 22 and 24, and 22 and 25 will not have any immediate effect upon the energizing circuit of the relay 20 s the contacts 44 and 45 will remain open and it will be impossible to complete any electrical circuit by the contacts 22 and 25, or

burner-e 'by;;the::photocell :l 3 so.:that the :flame detector .40 does not energize z-rel-ay' 42, thecontacts of .l the-relay 42 will remain. in. the-positionin Figure ;1.-.. This ;will mean that theenergizing circuit -forrthe relay-20 will. be continued through the-.-heaterz24.

Continued. energization. of the heater 34- will v causethebimetal 33 .to move out from .under the contacts-3 l and-.32, andthe :contacts will open.

When the .contactst I and32 open, the energizing v circuit forthearelay 2t,- will be broken andthe apparatus :will. go to. a shutdownposition: and will remain in that position untillsuchitimea.asthe;

manual reset. button 35 .is;-.-depressecl topiace the contacted l and-..32 backcin. theeclcsedpgsition. so; that. aifurther startingattempt may; be made whemthe -.contacts.. of .theithermostatic device i 1 arerclosed...

contacts3l and 32 and thereiwill again be a shut-.. downas. explained above.

Itshould .b'enotedithat inboth .of the ..situations that. have beendescribed in connection. with the .flame. failure that upon the. opening of the safety switch contacts-3| .and 32 the energizingv circuit'td thehcater 34 is interrupted so that there. willbe .no. further. heating of. the heater and assoon as the bimetal'33 is cooled sufficiently, depressing of. the .start button. 35 .willrcause ..cu' ing of the contacts 3 i and 32;

Operation-upon-aifalse indication of flame:

Whenever a. situation-exists in the control apparatus. thatLthe flame detection.v relay -52 is in.. the energized positionwhen in fact thereis no. fla'mepresent at the burner it, it .isde'siredthat the apparatus be shut down and. be.maintained-.

in a. shutdown condition. until such. time as the fault causinglfalse-operation of therelay 42 has.

been removed. The need ;ior such an arrange mentcan be understood when it is noted that the flame detection. device 48 includes electronic discharge devices whichlnormally require anlappreciable period pf time .for heating. and. coming.

into operation. For pnrppsesof explanation as-. sume. there is no calllforheat and the flame detectiQn. device 40" has developed a fault'which' causes. the relay 42' to be energized when in fact nofiame'is presentat burner. 59; life. power failure. now occurs the electron discharge devices of flame "detectori iii cool and relay l2'ibecomes deenergized. When a burner control apparatus is used which doesnot have the component checking feature, upon a3 call for heatand the subsequentrestoration"otpower, due to theiact that the'fiame detection apparatusidincludes electron; discharge devices which. must be heated to their operating'temperature before relay 3-2 cairbe energized, the relay 42 Will"pullin after the relay Ziilhas pulled .in' as though the appa ratus were starting asin a, normal start with. the

relay pulling in first and the relay. 62 subse-v quently pulling; in to indicate the presence of burner flame.

To; protectlagainst; such conditions -,wher.ein;1

false; operation or the. flame; detectionrrelayyfl will permit operation: of the; system :without *adee quateflame supervision-,iaspecial circuit arrangement is provided :fOI: energizingthe safety switch I heater. 34 wheneverthere i363. f false :operation of the relay 42-.-when-. there is no. demand. for burner operation: by, the rthermostatia device H thus- Assume further. that there-isiaafalse. indication of .burnerlflame by the relay, 42 so that theerelay. is in the. energizedpfisitiOn; When the-relay flii is in the .deenergized. position, the .contacts.of-.the relay are as shown in the. drawing with-contacts: 22 and 25 closed and contacts 22 and.24-open. When the relay 42 is indicating the presence of flameitwillbe in the energizedipositionand when. energized thecontacts 4Q- andciwillibe closed. and. thecontacts it and. 4! will. be open; When contacts 64 and G5 are closed. and 22.and

25 are closed, an energizing circuit will be completed to the heater .34 and this energizing circuit may be traced from thetap IQ of secondary. Hi through the switch contact 44, switch contact 45,

switch contact 22, switch contact25; and heater. 34 back to the end terminalof the secondary-l1. As long as this circuit remains energized there will be heat supplied to the heater34 and,'aft'era predetermined time, the heater as will. cause contacts 3! and 32 to open. When the contacts open, it will be impossible to energize the relay 2% uponsubsequent closing'of the thermostaticv device H. t will be'noted that the energizing circuit for the heater 34 is independent of the contacts 3! and 32 under the present circumstances and even though the contacts 3| and 32 open, the heater 3 will remain energized and therefore the bimetal33*Wi11 remain'in a warped position so that it will be-impossibleto reclose the contacts 35 and'32 until such time as the energizing circuit to the heater 34'is broken:

This can be accomplished only by causing the relay 42 to move to a deenergized position and removing the fault which is causing the false operation of the relay. As'soon'as the fault causing false operation of the relay is removed, the apparatus can be operated as explained above during the normal operation.

Conclusion From the foregoing it will be seen that 'a burner control apparatus "has been provided which will shut down the burner in the event that there is a false operation of the flame "detection relay or a flame failure. It will also be noted th'at'the apparatus is so arranged'that when'operating normallyth'e electrical circuit to the heater 35* of the safety switch device 30 is open circuited" so that it is impossible for the. current to'flow therethrough. In prior component checking burner'control 'apparatus it is possible to 'en-" ergize the heater of the safety switch when the apparatus and burner are-functioning normally since 'the'safety switch heater is shorted instead of opencircuited; therefore, in theevent that the shortingicontacts become'contamin'ated or dirty sufii'cient current. will flow through the heater to cause .the safety switch to operate when im fact a flame is present atth'e burner beingcontrolled ;It should further.ibemoted that in theeventthat 7 if the contacts of the relay 42 become contaminated so that when contacts 46 and 41 should be engaging upon a flame failure when the relay 42 moves to the deenergized position, it will be impossible to establish an energizing circuit for the relay 2! as the moving of the relay 42 to the deenergized position causes opening of the contacts 44 and 45 and this will deenergize the relay 20. When relay 20 is deenergized the contacts 22 and 24 will open so that the only energizing circuit for the relay 20 has to be through the contacts 46 and 41. If these contacts are not making proper electrical contact it will be impossible to energize the control relay 20.

Inasmuch as many modifications to the present apparatus can be made by one skilled in the art without departing from the teachings thereof, it is intended that the scope of the invention be limited solely by the appended claims.

I claim as my invention:

1. Control apparatus for a fuel burner, comprising, a source of power, a control relay having a relay coil and a first pair of switch contacts which are closed when the relay coil is deenergized and a second pair of switch contacts which are closed when the relay coil is energized, said relay adapted to cause energization of the fuel burner upon becoming energized, a safety cutout device having means including a heater arranged to open a pair of safety contacts after a predetermined period of energization, a combustion responsive switching mechanism having a pair of contacts which are closed when there is no combustion and a pair of contacts which are closed when there is combustion, said contacts of said switching mechanism being overlapping with changing position, an energizing circuit for said relay coil including said source of power, said. heater, said pair of contacts of said switching mechanism which are closed when there is no combustion, and said pair of safety contacts, a holding circuit for said relay coil when combustion is present including a portion of said source of power, said second pair of switch contacts of said control relay, and said pair of contacts of said switching mechanism which are closed when there is combustion, said heater being open circuited when said pair of contacts of said switching mechanism, closed when no combustion is present, are opened, and an enermeans and having a first pair of contacts closed when said relay contact actuating means is deenergized and a second pair of contacts which are closed when the relay contact actuating means is energized, means controlled by said relay adapted to complete an energizing circuit for the fuel burner when said relay is energized, a source of power having two end terminals and a tap, a combustion responsive switching mechanism having a first pair of contacts closed when no combustion is present and a second pair of contacts closed when combustion is present, a safety cutout device having an electrical actuator and a pair of cutout contacts, a circuit for connecting said end terminals of said source of power in energizing relation to said relay contact actuating means including said pair of cutout contacts, the first pair of contacts of said switching mechanism, and the actuator of said cutout device, a holding circuit for connecting said relay contact actuating means to said tap and one end terminal of said source of power and including the second pair of contacts of said control relay and the second pair of contacts of said switching mechanism, and an energizing circuit for the actuator of said cutout device when there is a false indication of combustion including said source of power, the second pair of contacts of said switching mechanism, and the first pair of contacts of said relay.

3. Control apparatus for a fuel burner, comprising, a control relay having contact actuating means and having a first pair of contacts which are closed when said relay contact actuating means is deenergized and a second pair of contacts which are closed when the relay contact actuating means is energized, means controlled by said relay adapted to complete an energizing circuit for the fuel burner when said relay is energized, a source of power having two end terminals and a tap, a combustion responsive switching mechanism having a first pair of contacts which are closed when no combustion is present and a second pair of contacts which are closed when combustion is present, a safety cutout device having an electrical actuator and a pair of cutout contacts, a circuit for connecting said end terminals of said source of power in energizing relation to said relay contact actuating means including said pair of cutout contacts, the first pair of contacts of said switching mechanism, and the actuator of said cutout device, a holding circuit for connecting said relay contact actuating means to said tap and one end terminal of said source of power and including the second pair of contacts of said relay and the second pair of contacts of said switching mechanism, the actuator of said cutout device when said holding circuit is complete being electrically open circuited to prevent further energization thereof, and an energizing circuit for the actuator of said cutout device when there is a false indication of combustion including said source of power, the second pair of contacts of said switching mechanism, and the first pair of contacts of said relay.

4. Control apparatus for a fuel burner comprising, a control relay having contact actuating means and having a first pair of contacts which are closed when the relay contact actuating means is deenergized and a second pair of contacts which are closed when the relay contact actuating means is energized, means controlled by said relay adapted to complete an energizing circuit for the fuel burner when said relay is energized, a source of power having two end terminals and a tap, a combustion responsive switching mechanism having a first pair of contacts closed when no combustion is present and a second pair of contacts closed when combustion is present, means connecting the first and second pair of contacts of said relay to electrically separate the first pair of contacts of said switching mechanism from the second pair of contacts of said Switching mechanism, a safety cutout device having an electrical actuator and a pair of cutout contacts, a circuit for connecting said end terminals of said source of power in energizing relation to said relay contact actuating means including said pair of cutout contacts, the first pair of contacts of said switching mechanism, and the actuator of said cutout device, a holding circuit for connecting said relay contact actuating means to said tap and one end terminal of said source of power and including the second pair of contacts of said relay and the second pair of contacts of said switching mechanism, and an energizing circuit for the actuator of said cutout device when there is a false indication of combustion including said source of power, the second pair of contacts of said switching mechanism, and the first pair of contacts of said relay.

5. In a burner control apparatus, a source of power, a safety switch device having a pair of switch contacts and a heater therefor which is operative to cause opening of said safety switch contacts upon continued energization for a predetermined length of time to eifect deenergization of said control apparatus, a thermostatic switch adapted to be closed upon indication of a need for burner operation, a first relay having in and out switch contacts, said relay adapted to cause energization of the burner upon becoming energized, a second relay having overlapping in and out switch contacts, said second relay normally being rendered operative upon proper operation of the burner, a first electric circuit for energizing said first relay, said circuit including said thermostatic switch, said safety switch contacts, the out switch contacts of said overlapping switch contacts, said safety switch heater and said source of power, a second electric circuit for maintaining said first relay energized independently of said safety switch heater and adapted to be completed without interruption of the energization of said relay, said second circuit including said thermostatic switch, the in contacts of said overlapping contacts, in contacts of said first relay and said source of power, and a third electric circuit adapted to be completed through said safety switch heater upon said first relay becoming deenergized and said second relay remaining in energized position, said third circuit including the in contacts of said overlapping contacts, out contacts of said first relay, and said source of power.

6. In a burner control apparatus, a source of power, a safety switch device having a pair of switch contacts and a heater therefor which is operative to cause opening of said safety switch contacts upon continued energization for a predetermined length of time to efiect deenergization of said control apparatus, a control circuit adapted to be closed upon an indication for need of operation of the burner, a first relay having in and out switch contacts, said relay adapted to cause energization of the burner upon becoming energized, a second relay having overlapping in and out switch contacts, said second relay normally being rendered operative upon proper operation of the burner, a first electric circuit for energizing said first relay, said circuit including said control circuit, said safety switch contacts, the out switch contacts of said overlapping switch contacts, said safety switch heater, and said source of power, a second electric circuit for maintaining said first relay energized independently of said safety switch heater and adapted to be completed without interruption of the energization of said relay, said second circuit including said control circuit, the in contacts of said overlapping contacts, in contacts of said first relay, and said source of power, and a third electric circuit adapted to be completed through said safety switch heater upon said first relay becoming deenergized and said second relay remaining in energized position, said third circuit including the in contacts of said overlapping contacts, out contacts of said first relay, and said source of power.

JOHN E. LUNDBERG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,108,770 Kriechbaum Feb. 15, 1938 2,537,291 Wilson Jan. 9, 1951 2,537,292 Wilson Jan. 9, 1951 2,537,294 Wilson Jan. 9, 1951 2,537,295 Gille Jan. 9, 1951

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